The present invention relates to a hydraulic accumulator, particularly a hydraulic damper, having a connecting piece providing fluid communication between the hydraulic accumulator interior and fluid connecting lines in a connection fitting. The connecting piece is connected to the connection fitting and the accumulator housing.
Pressure fluctuations can occur in hydraulic systems, involving periodic or even singular occurrences. Cases frequently arise involving discharge flow fluctuations of rotary pumps, operation of blocking and regulating valve systems with short opening and closing cycles, and connection and disconnection of pumps, as well as sudden impact-causing connecting of fluid chambers having different pressure levels.
Hydraulic dampers are adapted to the hydraulic accumulator, and serve for the damping of such pressure fluctuations (DE 25 08 960 A1, DE 36 09 534 C1), whereby the use of membrane or diaphragm and bubble accumulators is particularly suitable. Furthermore, the hydraulic dampers according to the type of construction differ from one another in terms of pulsation dampers, suction flow stabilizers, pressure surge dampers and liquid sound insulation dampers or silencers. More detailed individual features concerning these different types of constructions are the subject of the published brochure xe2x80x98Hydraulic dampersxe2x80x99, in No. 3.701.7/7.95 of the Hydac Catalog 01, under Heading 4.
In known damping solutions using hydraulic accumulators or hydraulic dampers, as disclosed, for example, on page 14 of the above-identified Hydac Catalog, a bubble or membrane/diaphragm accumulator is connected through an adapter or connection member with two fluid connecting lines in the form of tubular lines. The tubular lines extend essentially in a plane. The connecting piece opens in the area of the tubular connecting lines at a right angle thereto, with these lines being part of a connection fitting. In this manner the fluid chamber of the accumulator, consequently the interior of the accumulator, is connected with the fluid connecting lines. When the above described pressure fluctuations are considered, the gas chamber of the accumulator is intended to quench such pressure impacts. Particularly nitrogen is to be used in this case as working gas.
DE-A-3 235 234 discloses a low cost hydraulic accumulator whose pressure vessel includes a spherical body. In the pressure vessel, a bubble support part can completely support the membrane bubble, insofar as the interior of the bubble support system remains clear of fluid. For the attachment of the hydraulic accumulator to a fluid supply, the bubble support part has on its bottom a connection piece with an axially symmetrical connecting journal. The connecting journal is provided with an exterior threading for the screwing into a corresponding attachment member. The attachment member carries the fluid supply for the hydraulic accumulator. This hydraulic accumulator, taking this into consideration, has only one fluid attachment extending in the longitudinal direction of the bubble support part, and consequently, requires a quite extensive structural space. Since this hydraulic accumulator is accessible through only one fluid attachment to its connection piece, unfavorable pressure behaviors occur in the system, which particularly is the case insofar as such an accumulator is to be used as damper, stabilizer or the like.
U.S. Pat. No. 4,877,055 discloses a throttle valve connected in a hydraulic circuit with a hydraulic accumulator such that when use of the hydraulic accumulator is not required, its fluid stored on the fluid side is provided continuously through the one leak-point-forming throttle valve to the tank side, to attain a complete relaxing of the elastic membrane in the hydraulic accumulator. Damage to the membrane is avoided in such a slackened membrane state, even long-term.
The leakage structure comes into usexe2x80x94throttle valve is in the cartridgexe2x80x94and engages over its axially symmetrical connection piece with exterior threading in a connection fitting with two fluid connections for the hydraulic circuit. In the connection piece, a throttle part is mounted with its exterior wall limiting an annular channel, and otherwise is surrounded by the interior wall of the connection piece. A connecting section of the one fluid connection can be attached to the hydraulic accumulator, and then opens in screwing-in direction of the connection piece into the aforementioned annular channel. The annular channel in turn opens through a fluid connection on the tank side into the connection piece. Even that throttle-valve arrangement is of large construction in its longitudinal design, particularly because in order to attain an effective throttle point for the fluid, such a large gap area is provided between connecting piece and throttle part, which is slackened in the direction of the annular channel. Also such arrangement, with its corresponding long fluid line extension, allows no favorable pressure behaviors in the area of the total system with hydraulic accumulator. Also, in the area of attachment and connection piece, it is of large construction.
Objects of the present invention are to provide a hydraulic accumulator, particularly a hydraulic damper, which facilitates compact installation, uses fluid connecting lines of short length, and thus, facilitates an improvement of the control of the pressure behavior in the system and improves the potential for exchange by limiting the repair cost.
The foregoing objects are basically provided by a hydraulic accumulator having a connecting piece providing fluid communication between the hydraulic accumulator interior and fluid connecting lines in a connection fitting. The connecting piece is provided on its exterior periphery with at least one annular channel. A connecting section of the connecting piece opens into the interior of the hydraulic accumulator and the annular channel, providing fluid communication between the associated fluid connecting line in the connection fitting and the accumulator interior. The connecting section opens at a right angle to the screwing-in direction of the connecting piece into the annular channel. An additional connecting section in the connecting piece provides fluid communication between the accumulator interior and the other connecting line in the screwing-in direction. The hydraulic accumulator or hydraulic damper, with its connecting piece, can be fitted directly into the connection fitting, and particularly, can be screwed together with the connecting piece in such a manner that a compact installation is attained.
On the basis of this compact arrangement, the connecting section opens at a right angle into the annular channel. Also, the connecting line lengths in the design of the connection sections are shortened within the connection fitting. Thus, harmful pressure differentials are reduced and the pressure fluctuations can be better damped. Furthermore, an installation can be mounted, for example, directly at the source of the disturbance, for example, directly on the pump which produces the pressure fluctuations. Because of the integral construction of the connecting piece and the accumulator housing being directly engaged in the connection fitting, greater security during assembly can be attained, since fewer structural parts are being used. Also, such hydraulic accumulator can, in a simple operation, be removed from the connection fitting, so that a simpler, lower cost exchange of the hydraulic accumulator is possible.
One particular difficulty for the intended block construction lies in the exterior design and the simultaneously required positive guiding in the interior through the connecting piece of the hydraulic damper. That problem is preferably solved by the connecting piece of the hydraulic damper being configured as an axially symmetrical connection journal with exterior threading.
A particularly compact construction of the arrangement is attained when, preferably, the second connecting section opens into a separate annular channel extending on the exterior periphery of the connecting piece of the hydraulic accumulator and arranged in the screwing-in direction in a different plane form the first annular channel. Furthermore, the arrangement can provide that the other fluid connection line opens transverse to the direction of screwing-in into the other annular channel carrying fluid.
With another particularly preferred embodiment of the hydraulic accumulator of the present invention, the connecting sections open as fluid lines mounted in at least one enlarged hollow space of the connecting piece. This arrangement in turn decreases the damaging delta-p in the feed and discharge lines. Preferably, the fluid connection line is configured as a connection block having standardizable fluid connection lines. In this case, a modular construction system of connection block constructions and the hydraulic damper can be manufactured at low cost.
In the case of one particularly preferred embodiment of the hydraulic accumulator of the present invention, its accumulator housing rests on the connection fitting, or maintains a certain axial distance from the connection fitting in the screwing-in direction. Between the housing and the connection fitting or between the connecting piece and the connection fitting only a jointing arrangement is arranged in the form of a sealing ring or a gasket. Since basically only one outwardly working seal is required, this arrangement simplifies and shortens the assembly outlay.
With another preferred embodiment of the hydraulic accumulator of the present invention, the connecting piece is provided with an additional jointing arrangement aligned along its exterior threading, or the connecting piece is provided at its open end with an installation cone or tapered socket. As a jointing arrangement, a plastic seal is provided solely on the exterior periphery of the exterior threading. Such arrangements are provided with a reduced jointing means or gasket insert, particularly for the situations wherein very high fluid velocities, or pulsations are in force. The screw threading, in turn, because of its considerable threading length, can be assumed as a seal arrangement for particular special uses.
A particularly low-cost and compact construction can be attained insofar as the hydraulic accumulator is embodied as a metal bellows accumulator. The bellow open end is turned toward the connecting piece. The bellows exterior periphery limits a fluid chamber with the housing. Preferably, the housing is likewise configured as the metal bellows, which is itself axially symmetrical.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.